Operating principle of a capacitive touch pad is that: a capacitive sensing panel is a small area of electrode (the electrode plate can be in a shape of rectangle, a triangle, a circle and the like) which is in connection with a capacitive sensing path of a capacitance sensing module via a wire, so that the small area of electrode can form a low-voltage electric field in an electric conductor; when touching or closing the capacitive panel, owing to the electrical field on human body, a coupling capacitance can be formed between fingers and a conductive layer so that a flow of current is implemented between the capacitive sensing panel (electrode) and the capacitive sensing path of the capacitance sensing module, and then the capacitance sensing module can convert to a corresponding value of sensing capacitance in accordance with the change of the current; the whole touch pad is formed of a plurality of small sensing panels arranged in a certain layout, and thus touch positions can be accurately calculated according to the value of capacitance of each small panel (each capacitive sensing path) and the layout thereof.
The touch pad and the sensing electrode can be made of PCB and circuit wiring. Generally, the wiring of the sensing electrode is disposed on the top layer with an additional non-conductive protective layer. In comparison with a common resistive touch pad, the capacitive touch pad becomes more and more popular and has been used more and more widely due to the reasons that it has a faster speed of response and is able to support various technologies, such as the multiple touch technology and the like.
To apply the capacitive touch pad to electronic equipment, a higher grade of single-chip microcomputer, such as a 16 bit or 32 bit single-chip microcomputer, needs to be used in a general design so that the capacitive touch pad can have a good performance and representation effect. These high-end single-chip microcomputers can be the chips of ARM series or MIPS series, and the like. However, these kinds of the chips of the single-chip microcomputers are very expensive and have relatively higher power consumption, which result in the increase of manufacture cost and the need of equipping with a compatible power supply module with high capability. Accordingly, the electronic equipments which are able to apply for the capacitive touch pads at present are only limited on the high-end application facilities manufactured by several large manufactures. Therefore, the capacitive touch pads are not suitable to be used in ultra-low power consumption (the current consumption is lower than the level of tens of microampere (uA), even lower than the level of a few microamperes) embedded equipments, such as a remote controller. With the diversified development of electronic equipments, it is desired to develop diversified application solutions suitable for more and more the low-end equipments. Therefore, there is a difficulty in combing an 8-bit single-chip microcomputer designed as master controller equipment with the capacitive touch pad.